The original sentence is fine; it means, "What do you think about the weather?" 〇〇をどう思いますか is the general pattern for "What do you think about _____?" It may seem strange if you translate it literally, but many idioms do.

By using omoimasu... Or in this case omoimasuka in the sentence you are asking a non-direct question. From what I remember, the Japanese do this so as not to pigeonhole someone into 'having' to answer a question a certain way.. By asking what do you think, you give the other person a more broad spectrum to answer from than by saying How's the weather?

Less direct questions generally are more polite as well, but that's more inuendo than anything else.